Hasil untuk "Heat"

Carl Wu

M. Ozisik

D. Parsell, A. Kowal, M. Singer et al.

M. Kedaria, T. Menovsky

S. Kakaç, Hongton Liu

E. Candido

Xiao-feng Peng, G. Peterson

A. Pockley

Saeed Shiri, Holger Schubert, Benjamin Hilpert et al.

This study investigates short-pulse high-current resistance spot welding (RSW) of DH1200, a third-generation advanced high-strength steel (AHSS) critical to lightweight automotive structures. Six RSW scenarios were designed by varying weld time and current in both single- and double-pulse schedules, targeting a rarely explored regime with durations as short as ∼100 ms and currents up to 15 kA. Key weld attributes, including nugget size, microstructure, hardness, liquid metal embrittlement (LME) cracking, and tensile shear strength (TSS), were systematically analyzed. Contrary to conventional understanding, increased heat input did not necessarily generate larger nuggets or greater LME severity. Instead, weld current was found to be the dominant controller of nugget size, LME cracks, and TSS. Microhardness near the weld centerline was governed primarily by microstructure and remained largely insensitive to process parameters. Short-time, high-current conditions in double-pulse RSW produced large nugget sizes, exceeding even the 6sheetthickness criterion, and enhanced both TSS peak load and energy absorption. Furthermore, reducing weld time at constant current significantly mitigated LME, which caused substantial strength degradation in two severe cracking cases. These findings offer new insights into the development of short-pulse RSW schedules beyond conventional practice, enabling cycle-time reduction in automotive production.

S. Hajat, R. Kovats, K. Lachowycz

E. Rousseau, A. Siria, G. Jourdan et al.

Deyu Jiang, Miao Luo, Changxi Liu et al.

In this study, a Ti1.5Nb1Ta0.5Zr1Mo0.5 (TNTZM) high-entropy alloy was fabricated using laser powder bed fusion (LPBF). By integrating 63 sets of parameter trials with machine learning (ML) models, an optimised process window was identified, achieving a density of up to 99.9%. The combination of relatively high laser power and low scanning speed resulted in the formation of a stable cellular structure. Subsequent heat treatments at 700, 850, and 1000°C showed that while small-angle misorientations developed at cell-wall interfaces and medium-entropy (Ti–Zr–Mo) second-phase particles precipitated preferentially in the cell walls, the overall cellular architecture remained intact. Mechanical testing showed that these heat-treated samples exhibited yield strengths over 150 MPa higher than the as-built samples, while still retaining nearly 50% ductility under short-term heat treatment. In particular, small-angle grain boundaries and nanoscale second-phase particles together reinforce the cell walls and promote intracellular dislocation accumulation, thereby improving the overall mechanical properties of the alloy. These results demonstrate that combining ML-guided process design with targeted heat treatment is an effective method for additive manufacturing of refractory HEAs with high density and mechanical properties.

B. Agostini, M. Fabbri, J. E. Park et al.

H. Quan, Yu-xi Liu, Chang-pu Sun et al.

In order to describe quantum heat engines, here we systematically study isothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum versions of both the Carnot heat engine and the Otto heat engine are defined without ambiguities. We also study the properties of quantum Carnot and Otto heat engines in comparison with their classical counterparts. Relations and mappings between these two quantum heat engines are also investigated by considering their respective quantum thermodynamic processes. In addition, we discuss the role of Maxwell's demon in quantum thermodynamic cycles. We find that there is no violation of the second law, even in the existence of such a demon, when the demon is included correctly as part of the working substance of the heat engine.

Weerapun Duangthongsuk, S. Wongwises

S. Vandentorren, P. Bretin, A. Zeghnoun et al.

Xiaolong Gou, Heng Xiao, Suwen Yang

Si Chen, Yingting Luo, Gehao Sheng et al.

Abstract A slight turn‐to‐turn short‐circuit fault in the incipient stage does not trigger fuse protection, and the regular transmission and transformation functions of the transformer within the power grid are not affected very much by the incipient turn‐to‐turn short‐circuit fault. Therefore, the incipient turn‐to‐turn short‐circuit faults are often undetected, resulting in massive accidents. Incipient turn‐to‐turn short‐circuit faults lead to localized overheating in the transformer, which changes the transformer's oil‐tank surface temperature (OTST). A thermal simulation model (TSM) is presented. Based on the TSM, OTST data with different load rates and fault parameters are collected. The steady‐state and transient characteristics of OTST are analysed by extracting the OTST feature vector and the temperature difference of specific regions. The results show that the growth of the heat production value of faulty coils causes a rise in the OTST; higher faulty coils' locations lead to wider OTST differences; the temperature difference's area S can follow the incipient short‐circuit fault in the first 20 min after it occurs, which is faster than the top oil temperature. This study gives insight into the thermal behaviour of OTST, assisting in fault detection and location at the incipient fault stage.

Xiawei Yang, Mingxuan Yao, Yu Su et al.

In this paper, T-joints of Ti-6Al-3Nb-2Zr-1Mo titanium alloy were joined with friction stir welding, and microstructure evolution and forming mechanism were studied. The effect of using tungsten inert gas welding to heat additionally the FSW was investigated. Results show a strong effection microstructure of stir zone (SZ) due to the temperature gradient and fast cooling rate. The top and middle sections of SZ have a basketweave microstructure, while there is duplex microstructure at the bottom. When welding at 750 rpm-50 mm/min, the maximum tensile strength of the joint is similar to that of the base metal (BM). As the heat input increases, grain coarsening occurs, which reduces the joint tensile strength and the ability to plastically deform. The fracture mode changes from mixed fracture to ductile one. When TIG-assisted heat source is 20 mm in front of the tool and the power input is in 600 W, the temperature field produced is relatively uniform, which has a positive effect on the weld.

S. Sureshkumar, N. Rivals, P. Tamain et al.

Boundary plasma simulations are essential to estimate expected divertor and first wall (FW) heat and particle loads on ITER during burning plasma operation. A key missing feature of existing SOLPS simulations (Pitts et al., 2019) is the absence of a plasma solution out to the main chamber walls, essential to self-consistently estimate the gross sputtering of wall material. Here, SOLEDGE3X is applied for the first time to obtain up-to-the wall burning plasma solutions of the ITER boundary plasma at the nominal PSOL = 100 MW of the main SOLPS database simulations, including He ash, Ne seeding but without fluid drifts. Compared with the most recent SOLPS-ITER simulations, our simulations show differences in the exact impurity distribution, but the key results for divertor and wall heat flux remain consistent. In the context of the ITER re-baselining exercise (Pitts, 2024), in which the Be FW armour is proposed to be exchanged for tungsten (W), estimates of W wall sources are key to the assessment of likely core contamination and hence impact on fusion gain. We compare the W gross erosion rates due to the different species excluding W self-sputtering. For the cases simulated spanning 0.27%–0.47% separatrix-averaged Ne concentration and 7.5×1022s−1−1.95×1023s−1 D fuelling, Ne8+ remains the largest contributor to the sputtering flux with the largest source being the outer divertor and baffle. The species-wise contribution to W sputtering changes with fuelling with sputtering due to lower Ne charge states being significant at low D fuelling. In general, the gross W sputtering source is found to decrease with increase in D fuelling and increase with increased Ne seeding.